A base station based communication system according to the related art is defined by communication between a base station or an entity equivalent to the base station and a mobile station, and all activities of communication are controlled by the base station or the entity equivalent to the base station. For example, the base station controls all activities of the mobile station, such as a data transmission power of the mobile station. In other words, according to the base station based communication system, the base station controls operations of all the mobile stations under predetermined rules to obtain maximum throughput. However, these rules may be inefficient depending on applications or channel status of the mobile station.
For example, in a state that the mobile station is included in a shade zone, if the mobile station performs communication with the base station through a neighboring mobile station having a good channel status, power efficiency and communication throughput of the mobile station may be improved. However, since a communication service should be provided to the mobile station through the base station in the current base station based communication system, a problem occurs in that the advantages of power efficiency and communication throughput cannot be obtained.
Also, according to the related art, since the mobile stations should perform communication with their neighboring mobile stations through the base station, they consume more power. In other words, an irrational communication structure is caused, in which communication data should be transmitted to a destination mobile station through the base station, even if communication is to be performed between neighboring mobile stations close to each other.
However, although the conventional base station based communication system does not allow direct communication between mobile stations, the conventional system supports a structure similar to the direct communication. For example, the mobile station may transmit and receive data to and from the base station through a relay node without performing direct communication with the base station. If the relay node is used, the mobile station may obtain higher spectral efficiency with smaller power than the power used by the mobile station to directly transmit data to the base station.
However, the greatest problem of the relay node is that the relay node is not the mobile station and operates as an access point for connection to a network. In other words, if the mobile station intends to transmit data to its neighboring mobile station, there is a load in that the mobile station should transmit data to the relay node. Also, although the relay node may be installed more easily than the base station, it has limitation in removing a shade zone and extending coverage in that it should be connected with the base station through a predetermined backbone network and has no mobility.
In order to solve the above problem, a method for supporting high rate transmission of large capacity data and performing direct communication between mobile stations having a good channel status to remove a shade zone and extend coverage has been suggested. The communication between mobile stations may be referred to as direct communication between mobile stations or cooperative communication between mobile stations in accordance with purpose of use for communication. The direct communication between mobile stations means that, if there is user data to be transmitted from a mobile station A to a mobile station B, the user data is transmitted to the mobile station B without passing through a base station. The cooperative communication between mobile stations means that, if a channel status between the mobile station A and the base station is not good, communication between the mobile station A and the base station is performed through the mobile station B having a good channel status with the mobile station A and the base station.
Currently, studies on communication between mobile stations are mainly ongoing for a transmission scheme or a method for grouping mobile stations joining in direct communication. In particular, most of studies are ongoing in such a manner that a new transmission scheme is suggested and the suggested transmission scheme has performance more improved than that of the related art schemes under a specific status. In other words, most of studies are ongoing on the assumption that all the mobile stations already know information required for communication between mobile stations. On the other hand, studies on initiation procedures of communication between mobile stations have been relatively little performed, wherein the studies on the initiation procedures include studies on how communication between mobile stations is performed, how communication between mobile stations is controlled by a base station, etc., and how information on neighboring mobile stations is collected to be transmitted to a base station.